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Etude prospective des impacts sociaux d’une inondation majeure en région Ile-de-France.

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Disparités socio-spatiales dans la prise en charge des populations franciliennes en situation de crise et post-crise : une analyse cartographiée et quantifiée des besoins des ménages, de l’évacuation à la reconstruction.

06/08/2018

This doctoral thesis in geography and space planning addresses the social impacts of a major flood in Ile-de-France region (France). Social impacts relate to the effects of a flood on populations and their living situations. The thesis meets three different but complementary objectives: (1) the assessment on a GIS of social needs in the hypothesis of a massive evacuation; (2) a qualitative study of the ability of authorities to take care of populations in a crisis management situation; (3) the mapping of long-term social impacts and the assessment of recovery and reconstruction needs.
Our methodology relies on a hybrid approach, mixing statistical and GIS analyses on one part, and qualitative analyses on the other part. On the one hand, census data are processed so as to identify populations on a social and demographic level. It is essential in order to caracterize their needs during the different phases of a flood, from evacuation and sheltering to the process of recovery and reconstruction. As such, this study is based upon a state-of-the-art on past disasters, which identifies predictors of the behavior of populations during and after a disaster. Our GIS and statistical analyses lead to the mapping of synthetic indexes, aiming at representing the population ability to evacuate and to find a shelter by their own means, on the short term, and to recover on the long term. Theses indexes are then crossed to hazard data, applied to major flood scenarios. On the other hand, qualitative data from diverse sources (interviews, observations, written material) are decribed and interpreted in order to identify the means et strategies planned by the local and regional authorities to take care of their populations during a major flood. By comparing means, through qualitative analyses, and numerical and mapped social needs, through GIS and statistical analyses, one is able to caracterize the social impacts of a flood in Ile-de-France region.
Results are presented in the context of a geographic approach, through a series of maps available from regional scale to local scale. On the short term during the flood, up to 700,000 people could be evacuated and 120,000 sheltered, for a flood similar to the 100-year flood of 1910. 1,100,000 people would be evacuated, 200,000 sheltered, for a flood superior to the 1910 flood. On the long term, many structures and infrastructures crucial for the livability of the city could be damaged, with striking geographic inequalities. A dozen of municipalities with over 10,000 inhabitants would exceed the damage threshold of 30% of their structures and infrastructures, while some of them feature a weak recovery and reconstruction capability. Results also highlights the temporal aspect of vulnerability. Vulnerable populations during the evacuation step may not be the same during the sheltering step, or the recovery and reconstruction phases. In the same way, geographic inequalities, between departments, between municipalities, greatly vary according to the stakes, from massive evacuation to reconstruction.

 

Activities Services CCR

Etude prospective des impacts sociaux d’une inondation majeure en région Ile-de-France.

Disparités socio-spatiales dans la prise en charge des populations franciliennes en situation de crise et post-crise : une analyse cartographiée et quantifiée des besoins des ménages, de l’évacuation à la reconstruction.

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